Historically, ion exchange resins (bead form) and ion exchange membranes have customarily been prepared by the copolymerization of a divinyl monomer; such as nonpolar, water insoluble divinylbenzene or ethylene glycol dimethacrylate (EGDM) with a monomer already containing ion exchange groups, such as 2-sulfoethyl methacrylate (2-SEM), or a monomer which after polymerization is convertible to contain ion exchange groups, such as styrene (convertible to sulfonated styrene) or dimethylaminopropylmethacrylamide (DMAPMA) (convertible to a quaternary ammonium halide after treatment with methyl chloride).
A technical difficulty often encountered is when one attempts to formulate a polymerizable mixture containing a nonpolar (usually water insoluble), monomer containing multiple vinyl groups; together with a highly polar (hydrocarbon insoluble)vinyl monomer such as the quaternized version of dimethylaminoethylmethacrylate (DMAEMA).
The monomers cannot be blended together prior to polymerization because of differences in polarity. A case in point is the hopeless task of copolymerizing divinyl benzene with any quaternary ammonium halide acrylate or methacrylate monomer. It is not feasible to combine divinyl benzene and very polar ionogenic monomers with any solvent capable of supporting both monomers in suspension for the preparation of ion exchange beads. It doesn't matter whether or not the solvent is a water medium or organic non-polar medium; the two monomers will not co-polymerize to form ion exchange resin beads since they are incompatible.
Because of the incompatibility customarily found between hydrocarbon or other water insoluble crosslinking agents and ionogenic (ion containing) monomers already in posession of their ion exchange groups; it has been difficult to prepare ion exchange polymers having the desired properties of:
1) Selective ion exchange capacity (i.e. the synthetic luxury of adding a fixed mole fraction of ion exchange groups during the copolymerization of network polyelectrolytes; PA0 2) Chemical and physical stability by allowing the synthesis of a highly crosslinked polymer having ionogenic groups and also caustic or oxidative stable groups in desired quantities in the co-polymerized network polyelectrolyte polymer; PA0 3) Gaining the advantage of having the crosslinker itself donating a portion of the ion exchange group concentration during polymerization; PA0 4) Having an anion exchange resin bead or membrane having essentially all polymerized crosslinker without the need to chemically functionalize the finished crosslinked structures (via a post chemical reaction) which always tends to weaken the surface of the resin bead or membrane plane structures; PA0 5) The preparation of highly crosslinked anion exchange membranes with very low water content. Such membranes are permselective to mineral acids (i.e. hydrochloric, nitric and sulfuric) and thus retain their permselective efficiencies for acids during the electrodialysis of salt acid mixtures. Such membranes are called acid efficient membranes; PA0 6) The easy and fast preparation of mixed charge ion exchange resins (beads) or membranes having salt absorbing-desorbing properties. These are called ion-retarding resins or membranes. PA0 1) Chlorine oxidation. PA0 2) Caustic degradation. PA0 3) Organic fouling. PA0 4) Theoretical surface polarization (in the case of ion exchange membranes) and PA0 5) Donnan dialysis (lack of acid permselectivtiy). PA0 R.sub.1, R.sub.2 = methyl or higher alkyl group. PA0 R.sub.3 = alkyloxy or alkylimino group. PA0 R.sub.4 = benzyl or alkyl group. PA0 1) A crosslinked anion exchange resin bead(s) containing ionogenic groups on both the crosslinker and on the mono vinyl monomer. PA0 2) A crosslinked ion exchange membrane (preferably supported by a fabric) containing ionogenic groups on both the crosslinker and the mono vinyl monomer. PA0 3) Either of the above created by polymerization of only the anion exchange bifunctional crosslinker.